The power to the gridseeds is via seperate 12V power supply. USB is only for data.
Are you *sure* the hub reads "12V"?
![Wink](https://bitcointalk.org/Smileys/default/wink.gif)
USB standard is 5 Volt.
This sounds like a cgminer problem to me. Have you tried asking in their support thread? I you haven't yet, make sure you provide more info, i.e. OS etc.
I'm sure there are also threads about setting up the gridseeds.